The effect of several catalysts on the synthesis of poly(ethylene furanoate) (PEF) was studied during a two-stage melt polycondensation process.

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In the present study, three new biobased furanoate polyesters with potential use in food packaging applications, named poly(isosorbide furanoate) (PIsF), poly(methyl-propylene furanoate) (PMePF) and poly(1,4-cyclohexane-dimethylene 2,5-furanoate) (PCHDMF) were synthesized. As monomers for the preparation of the polyesters, 2,5-furandicarboxylic acid (FDCA) and diols with irregular or complicated structure were used, including isosorbide (IS), 2-methyl-1,3-propanediol (MPD) and 1,4-cyclohexane-dimethanol (CHDM). The polymerization process was carried out via melt polycondensation method. The structural characteristics and thermal behavior of the polymers were studied. The kinetic fragility of the amorphous phase of the polymers was evaluated. The thermal degradation was studied by means of thermogravimetry and a pyrolysis Py-GC/MS (Pyrolysis-Gas Chromatography/Mass Spectroscopy) system to estimate the degradation mechanism.

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This study spotlighted a successful synthesis of a novel series of biobased poly(decamethylene-co-isosorbide 2,5-furandicarboxylate)s (PDIsFs) copolyesters from dimethylfuran-2,5-dicarboxylate (DMFD), isosorbide (Is), and 1,10-decanediol (1,10-DD) by melt polycondensation, using titanium(IV) isopropoxide (TTIP). The chemical structure and composition of prepared polymers were confirmed in detail by 1 H NMR and FTIR spectroscopies. Satisfactory weight-average molecular weights (M w ) in the 55,300−84,500 g/mol range and random microstructures were obtained for PDIsFs. It was shown that Is unit incorporation into the copolyesters molecular chains was dramatically effective in increasing the glass transition temperatures (T g ) and in delaying the onset decomposition temperatures of PDIsFs. Hence, an excellent improvement of the thermal stability exceeding 405 °C for all copolymers was obtained. In addition, the degradation behavior in soil as well as the mechanical properties of PDIsFs were duly investigated in detail. The biodegradation rate of the copolyesters depended on the comonomer ratio. Rotational rheometry characterization of polymer melts revealed prevailing viscous properties for all formulations, whereas the presence of isosorbide favored a Newtonian behavior. Oxygen induction time (OIT) measurements by chemiluminescence (CL) demonstrated that isosorbide incorporation also dramatically increases polymer thermo-oxidative stability. Taking advantage of their features, PDIsFs have the potential to serve as promising and innovative biobased polymers for practical applications such as ecofriendly and sustainable plastic packaging.

Abstract:The goal of this study was to synthesize, through a facile strategy, high molecular weight poly(ethylene furanoate) (PEF), which could be applicable in food packaging applications. The efficient method to generate PEF with high molecular weight consists of carrying out a first solid-state polycondensation under vacuum for 6 h reaction time at 205 • C for the resulting polymer from two-step melt polycondensation process, which is catalyzed by tetrabutyl titanate (TBT). A remelting step was thereafter applied for 15 min at 250 • C for the obtained polyester. Thus, the PEF sample was ground into powder, and was then crystallized for 6 h at 170 • C. This polyester is then submitted to a second solid-state polycondensation (SSP) carried out at different reaction times (1, 2, 3.5, and 5 h) and temperatures 190, 200, and 205 • C, under vacuum. Ultimately, a significant increase in intrinsic viscosity is observed with only 5 h reaction time at 205 • C during the second SSP being needed to obtain very high molecular weight PEF polymer greater than 1 dL/g, which sufficient for manufacturing purposes. Intrinsic viscosity (IV), carboxyl end-group content (-COOH), and thermal properties, via differential scanning calorimetry (DSC), were measured for all resultant polyesters. Thanks to the post-polymerization process, DSC results showed that the melting temperatures of the prepared PEF samples were steadily enhanced in an obvious way as a function of reaction time and temperature increase. It was revealed, as was expected for all SSP samples, that the intrinsic viscosity and the average molecular weight of PEF polyester increased with increasing SSP time and temperature, whereas the number of carboxyl end-group concentration was decreased. A simple kinetic model was also developed and used to predict the time evolution of polyesters IV, as well as the carboxyl and hydroxyl end-groups of PEF during the SSP.

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A series of blends of furan‐based green polyesters, for eco‐friendly packaging materials, are synthesized. Poly(ethylene 2,5‐furandicarboxylate) (PEF), poly(propylene 2,5‐furandicarboxylate) (PPF), and poly(butylene 2,5‐furandicarboxylate) (PBF) are synthesized by applying melt polycondensation. Blends of the above polyesters with 50/50 w/w composition as well as blends of furanoate/terephthalate (PPF/PPT) are also prepared. The glass temperature along with the crystallization and melting behaviors of melt quenched blends are studied aiming at understanding their dynamic state and miscibility. Based on their Tg and crystallization behavior, PEF/PPF shows dynamic homogeneity and miscibility whereas PPF/PBF and PEF/PBF exhibit partial miscibility and immiscibility, respectively. In an effort to dynamically homogenize the compounds, reactive blending is applied and the behavior of the resulting blends is monitored following quenching. A profound improvement in blend homogenization is observed with increasing melt mixing time for the PPF/PPT sample, evidenced by the single glass temperature and by the narrowing in liquid‐to‐glass regime. The obtained single glass temperature together with the suppressed tendency for crystallization with increasing mixing time are taken as evidences of dynamic and thermodynamic homogeneity.